Evidence of interactionPending medical review

The short answer

Yes, there is some evidence that karela adds to diabetes medicines. In a 2026 study, 70 people whose sugar was above target on metformin plus dapagliflozin added a standardised karela (bitter gourd) extract for three months. Their average HbA1c, a measure of sugar over about three months, fell from 6.93% to 6.34%. The study was not randomised, and its summary does not report low-sugar episodes.

We found no human study of karela with insulin or sulfonylureas such as glimepiride, where low sugar is the bigger worry. In rats, karela with glibenclamide had a stronger effect than the drug alone. If you take diabetes medicine and want to add karela juice, powder or capsules, tell your doctor and ask whether to check your sugar more often.

Common diabetes medicines in India include Glycomet (metformin), Amaryl (glimepiride), and the insulins Actrapid and Lantus.

At a glance

What was seen	How it may work	Direction	Evidence
Lower HbA1c when karela extract was added to metformin plus dapagliflozin[1]	Extra sugar lowering on top of the drugs	Sugar falls further; how often it falls too low is not known	Observational
Karela alone lowered fructosamine, less than metformin did[2]	Not established	Sugar-lowering effect of its own	RCT
Benefit of karela alone uncertain across trials[3]	-	-	Systematic review
Karela with glibenclamide improved sugar control more than glibenclamide alone[4]	Not established	Stronger combined effect on sugar	Animal
May add to insulin; extract blocks the enzyme CYP2C9[5]	Added sugar lowering; CYP2C9 inhibition, relevant to glibenclamide and glimepiride	Possibly lower sugar and more sulfonylurea in the blood; not tested in people	Theoretical by mechanism

No listing is not a clearance. A missing interaction here never means a combination is safe.

The evidence, study by study

Real-world cohort study, 2026 Observational

After six months on metformin plus dapagliflozin 10 mg a day, 70 people whose sugar was still above target added a standardised karela extract for three months. Another 85 who were already at target carried on as before. In the karela group, average HbA1c went from 6.93% to 6.34%. The groups started at different levels of control and were not randomised, the abstract gives neither the karela dose nor side effects, and nobody took insulin or a sulfonylurea.[1]

Trial against metformin, 2011 RCT

People newly diagnosed with type 2 diabetes took bitter melon at 500, 1,000 or 2,000 mg a day, or metformin 1,000 mg a day, for four weeks. Fructosamine, a marker of average sugar, fell by 10.2 micromol/L on the highest karela dose and by 16.8 on metformin; the lower doses made no significant difference. Karela was compared with metformin here, not combined with it.[2]

Cochrane review, 2012 Systematic review

Four randomised trials with 479 people, lasting up to three months and mostly at high risk of bias. The products varied too much to pool the results. Karela did no better than placebo and showed no reliable advantage over metformin or glibenclamide, and no serious side effects were reported. The search ended in February 2012, so newer studies are not included.[3]

Rat study with glibenclamide, 2019 Animal

Diabetic rats were given glibenclamide, a sulfonylurea, with or without a karela fruit extract for eight weeks. The combination improved insulin and HbA1c more than glibenclamide alone. Animal results show the question is worth asking. They cannot tell us how often low sugar would happen in people.[4]

What your doctor may watch for

Home sugar readings and HbA1c after you add karela as a remedy.[1]
Low sugar, especially if you take insulin or a sulfonylurea such as glimepiride or glibenclamide. Memorial Sloan Kettering warns that bitter melon may add to insulin.[5]

What to tell your prescribing doctor

You can read this out, or show them this page:

“I am taking, or planning to take, karela (juice, capsules or powder, and how much) along with my diabetes medicine. In one study, karela extract lowered HbA1c further on top of metformin. Should I check my sugar more often, and what reading should make me call you?”

Withheld until review

Dose adjustments and any “no known interaction” clearance appear only after a vaidya on our medical board has reviewed this page. Why we hold these back

Questions people ask

Is eating karela sabzi the same as taking karela capsules or juice?

No study has compared them. The human studies used extracts or measured products, not cooked karela. Tell your doctor which form you use and how often.[1][2]

Is karela good for diabetes?

The evidence is mixed. In a four-week trial, the highest dose lowered a sugar marker, but less than metformin did, and a 2012 Cochrane review found too little good evidence to be sure. It is not a replacement for prescribed treatment.[2][3]

Evidence

Sources

Awaiting review by The Good Vaidya Medical Board. Prepared from the sources below and checked against each one.

Published 4 November 2026 · Last updated 4 November 2026

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Karela (bitter gourd) and diabetes medicines